This application claims priority of Korea patent Application No. 2000-54136, filed on Sep. 15, 2000.
(a) Field of the Invention
The present invention relates to an exhaust gas recirculation (EGR) system, and more particularly, to an improved exhaust gas recirculation system capable of controlling an amount of recirculating exhaust gas according to exterior temperature.
(b) Description of the Related Art
The EGR system is a system for recirculating a portion of exhaust gas to an intake part of an engine so as to reduce generation of nitrogen oxides (NOx). Typically, the EGR system comprises an EGR valve connecting the exhaust and intake manifolds and which controls an amount of recirculating exhaust gas according to a state of the intake manifold such that some of the exhaust gas flows into the intake manifold having a relatively lower pressure than the exhaust manifold, when the EGR valve is opened. There are two kinds of EGR valves, i.e., a pneumatic EGR valve using pressure difference between the intake and exhaust manifolds, and an electronic EGR valve using solenoid valves. The pneumatic EGR valve is used in small size engines requiring an EGR amount of 5xcx9c10% and the electronic EGR valve in relative large size engines requiring an EGR amount of 15xcx9c20%.
FIG. 1 is a schematic view of a conventional pneumatic EGR system. As shown in FIG. 1, intake air is supplied to an engine 20 via an air cleaner 12, throttle body 14 and intake manifold 18. The amount of intake air is adjusted by a throttle valve 16 arranged in the throttle body 14. The intake air is mixed with fuel in combustion chambers of the engine and the exhaust emission after combustion of the mixed gas is exhausted through the exhaust manifold 22. From an initial closed state, the EGR valve 26 opens by pressure difference between the intake and exhaust manifolds 18 and 22 of the engine 20 when the throttle valve 16 is closed, that is, the intake part pressure becomes lower than the exhaust part pressure such that a valve plate 23 moves upward by overcoming an elastic force of a spring 27 of the EGR valve 22 so as to open an EGR passage 24, resulting in exhaust gas flowing into the intake part. A reference numeral 28 indicates an EGR-back pressure transducer (EGR-BPT) valve which adjusts pressure level applied to the EGR valve 26.
However, this conventional EGR system has a drawback in that the structure is complicated and requires many parts. Also, the electronic EGR valve requires a complicated EGR logic system and gives much processing burden to a controller.
The present invention has been made in an effort to solve the above problems of the prior art.
It is an object of the present invention to provide an improved EGR system capable of adjusting an amount of exhaust gas recirculated into a combustion chamber according to exterior temperature.
To achieve the above object, an EGR system comprises an intake and an exhaust valve arranged in a cylinder head of an engine, a first link pivotally supported by the cylinder head using a first pivot member for actuating the intake valve, a second link pivotally supported by the cylinder head using a second pivot member for actuating the exhaust valve, and an EGR adjuster connected to a proximal end of the first link and contacting a lower surface of the second link for adjusting exhaust valve opening.